The ceremony in Madrid's Almudena Cathedral is one of several events being held around the city Tuesday in homage to the 191 people killed and nearly 2,000 injured in the attacks.

Elsewhere, people laid flowers and lit candles at the train stations and sites of the bombings.

The attackers targeted four commuter trains with 10 shrapnel-filled bombs concealed in backpacks during morning rush hour on March 11, 2004. Twenty-eight people, mainly from North Africa, went on trial in 2007 and 18 were convicted of taking part in the attacks.